1. Field of the Invention
The present invention relates to charging in a 3GPP network, and more specifically to the provision of interoperability between Diameter policy control and charging in a 3GPP network.
2. Background Art
The Internet Protocol (IP) is the dominant communications protocol in the world today. Statistics reveal that over 15% of the world's population has access to the Internet, and recent growth rates reveal that this figure will continue to grow at an exponential rate. One of the chief virtues of the Internet is that it provides interoperability on a massive scale, and thereby permits communication between widely different devices. Such devices include not only desktop computers, but also portable computing devices, such as laptop computers, personal data assistants (PDAs), smart phones and the like.
Modern day usage has witnessed a substantial growth in the transmission of multimedia services over the Internet. That trend will continue as users expect access to personalized interactive, multimedia services, on any of the above devices, and at any location. Consequently, such expectations have driven telecommunications providers towards an “all IP” architecture for the provision of services.
In order to meet such requirements on network infrastructures, the IP Multimedia Subsystem (IMS) has been proposed. IMS details an architectural framework for the delivery of multimedia services to mobile users, using Internet protocols. IMS is specifically referenced in the 3rd Generation Partnership Project (3GPP), which serves to merge the Internet and mobile communications worlds. Therefore, to facilitate the integration of the mobile world with the Internet world, IMS adopts as many as are applicable of the Internet protocols.
In a 3GPP IMS network, the Policy and Charging Rules Function (PCRF) controls policy and charging rules over the Gx interface, while on-line charging is controlled over the Gy interface. In the context of on-line charging, the expiration of a quota for a subscriber leads to certain anomalies. For example, upon the expiration of a quota during a subscriber session, the Policy and Charging Enforcement Function (PCEF) will send a Gy credit charging request (CCR) to the Online Charging System (OCS) to request more quota. However, if there is no additional quota available, the OCS will respond with a Credit Control Application (CCA) indicating the absence of quota, as well as provide an indication via the Final-Unit-Action Attribute Value Pair (AVP) in the CCA as to what the PCEF should do with the subscriber's session. Three possible alternatives exist via the Final-Unit-Action AVP, namely termination of the Packet Data Protocol (PDP) context, redirection of the traffic over the context, or restricted access via supplied packet filters.
However, such an approach has two major drawbacks. Firstly, the OCS is limited in what it is permitted to return via the Gy interface in response to the quota expiration. Specifically, it is limited to the three options of terminate, redirect, and restrict access. In particular, it cannot deliver a complete Policy and Charging Control (PCC) charging rule (as would be supplied via the Gx interface). The second major drawback is that the PCRF is unaware of the changed policy that has been delivered by the OCS via the Gy interface. As such, the PCRF ceases to be a centralized policy control function since it is completely unaware that the OCS quota has been exceeded. Consequently, the PCRF may make incorrect or incomplete policy decisions as a result of its complete knowledge.
Traditionally, these drawbacks have been resolved by combining the Gx and the Gy interfaces together, and thereby merging the PCRF and the OCS functions in the architecture. Indeed, the 3GPP revision 6 specifically advocated such an approach. However, the conventional wisdom runs counter to the desires that the PCRF and OCS are intended to remain separate functions. Indeed, different vendors are often associated with each of the PCRF and the OCS functionalities. In fact, history reveals that there has not been a lot of co-operation between vendors of these two functionalities within the 3GPP architecture.
What is needed is a solution to the quota expiration scenario that preserves the independence of the OCS and the PCRF functionalities, such that the PCRF retains its centralized policy control and can return a new PCC charging rule.